WHERE DOES SHIGA TOXIN COME FROM?

I helped develop this figure for an mBio commentary on the trafficking of Shiga (Stx) toxin during serious infections with entero-haemorrhagic E. coli (EHEC). This commentary was written because research had been published that caused the scientific community to re-visit what it knows about how the deadly Stx toxin spreads throughout the body during EHEC infection.

Shiga toxin is associated with serious blood and kidney disease and even death during EHEC infection, but the toxin is only made in EHEC because the bacterium has itself been infected with a virus (or bacteriophage) which carries a gene for the toxin. It is likely that bacteriophages try to infect our cells too, but this is really inefficient and doesn’t lead to any new bacteriophages being made, because bacteriophages are viruses that have evolved to target bacteria.

Previously it was thought that Shiga toxin only came from infecting bacteria and was absorbed by the gut into the bloodstream, where it could spread to the areas it causes the most damage in, the brain and the kidneys. The research by Bentecor et al. demonstrated that our own cells could recognise the bacteriophage’s toxin gene and make Shiga toxin from it. This commentary by Andreas Lengelinget al. discusses how this is relevant – if bacteriophages tried to infect our cells too, they may deliver tiny amounts of the toxin gene into our cells, and now we think that this toxin would be made.